Cooler and a method for cooling hot bulk material

ABSTRACT

The invention relates to a cooler and to a method for cooling hot bulk material. The hot bulk material is fed on a stationary aerating base through which cooling gas can flow and is transported by means of reciprocating conveyor elements disposed above the aerating base. In the cooler and cooling method, at least two groups of conveyor elements are used which are actuated jointly in the transport direction and separately from one another against the transport direction.

The invention relates to a cooler for cooling hot bulk materialaccording to the preamble to claim 1 and also to a method of cooling hotbulk material according to the generic concept of claim 9.

For cooling of hot bulk material, such as for example cement clinker,the bulk material is fed on a cooler grate through which cooling airflows. During transport from the start of the cooler to the, end of thecooler, cooling air flows through the bulk material thereby cooling it.

Various possibilities are known for the transport of the bulk material.In the so-called reciprocating grate cooler the bulk material istransported by movable rows of cooler grates which alternate withstationary rows of cooler grates in the direction of transport.

It is also known to provide a stationary aerating base, through whichcooling gas can flow, in order to receive the bulk material, withconveyor elements for transport of the bulk material above the aeratingbase. In the transport mechanism there is a distinction between rotatingconveyor elements and reciprocating conveyor elements.

A cooler according to the preamble to claim 1 is known from DE 878 625.The conveyor elements described there are formed by bars which aredisposed above a stationary grate and extend in the longitudinaldirection parallel to the plane of the grate. The bars are connected toa suitable moving mechanism which makes possible a reciprocatingmovement of the bulk material in the transport direction. In addition,suitable projections are provided on the bars in order to assist theconveying action.

In contrast to the rotating conveyor elements, in the case of thereciprocating conveyor elements the problem arises that some of the bulkmaterial is carried back with the return stroke. However, thisdisadvantage can be compensated for by a suitable design of the conveyorelements. Thus for example conveyor-elements are proposed with asubstantially triangular cross-sectional shape, in which the end facepointing in the transport direction is substantially perpendicular tothe transport direction and the rear end face encloses an angle between20 and 45° with the aerating base. Whereas in the forward stroke thesubstantially perpendicular end face achieves a good conveying action,in the return stroke the conveyor element can be drawn back under thebulk material due to its wedge shape.

Also with such a construction of the conveyor elements some of thequantity of bulk material is carried along with the return stroke.

The object of the invention, therefore, is to improve the cooleraccording to the preamble to claim 1 or the method according to thegeneric concept of claim 9 with regard to the conveying action.

This object is achieved according to the invention by the features ofclaims 1 and 9.

Further embodiments of the invention are the subject matter of thesubordinate claims.

The cooler according to the invention for cooling hot bulk material hasa stationary aerating base, through which cooling gas can flow, in orderto receive the bulk material and also has reciprocating conveyorelements disposed above the aerating base for transport of the bulkmaterial. The conveyor elements are provided in at least two groupswhich can be actuated jointly in the transport direction of the bulkmaterial and separately from one another against the transportdirection.

Particularly in the case of coarse bulk material, the bulk materialforms a relatively compact unit which can be moved with the jointforward stroke of the conveyor elements in the transport direction. Asthe various groups of conveyor elements are actuated individually andsuccessively with the return stroke, because of the friction conditionsin the material bed considerably less bulk material is carried alongagainst the transport direction than in the case of a joint return ofall conveyor elements.

Each group of conveyor elements consists of at least one conveyorelement or conveyor element line.

In a further embodiment of the invention it is also conceivable that theconveyor elements of a group can be actuated individually, so that theycan be actuated for example at different speeds and for differentlengths of time or with different strokes.

In a first embodiment the individual groups of conveyor elements areprovided so that they alternate transversely with respect to thetransport direction of the bulk material. In the tests on which theinvention is based it has been shown that the best results can beachieved with three groups of conveyor elements which are disposed sothat they alternate transversely with respect to the transportdirection.

In a second embodiment the conveyor elements which are adjacenttransversely with respect to the transport direction are disposed insuch a way that at each phase of the sequence of movements they areoriented offset from one another in the transport direction.

In a third embodiment according to the invention the individual groupsof conveyor elements are disposed so that they alternate in thetransport direction of the bulk material.

Because of the friction conditions in the region of the lateral limitsof the cooler or for reasons related to process engineering it may beadvantageous to design the stroke of the conveyor elements to be ofdiffering length over the width of the aerating base.

Further advantages and embodiments of the invention are explained ingreater detail with reference to the description of some embodiments andthe drawings.

In the drawings:

FIG. 1 shows a schematic longitudinal sectional representation of thecooler,

FIG. 2 shows a schematic cross-sectional representation according to afirst embodiment of the conveyor elements,

FIGS. 3a to 3 d show a schematic representation of the sequence ofmovements in plan view of the first embodiment,

FIG. 4 shows a schematic cross-sectional representation according to asecond embodiment of the conveyor elements,

FIGS. 5a to 5 d show a schematic representation of the sequence ofmovements in plan view of the second embodiment,

FIG. 6 shows a schematic cross-sectional representation according to athird embodiment of the conveyor elements, and

FIGS. 7a to 7 c show a schematic representation of the sequence ofmovements in plan view of the third embodiment.

The cooler 1 shown in FIG. 1 for cooling of hot bulk material 2essentially comprises a stationary aerating base 3, through whichcooling gas can flow, to receive the bulk material and alsoreciprocating conveyor elements 4, 5, 6 above the aerating base fortransport of the bulk material. The bulk material 2 is formed forexample by cement clinker which is delivered from a rotary kiln 7connected upstream of the cooler. The bulk material proceeds via anoblique inlet region 8 onto the stationary aerating base 3 where it istransported through the cooler in the longitudinal direction by means ofthe conveyor elements 4, 5, 6.

The aerating base is constructed in a manner which is known per se andin particular has openings through which the cooling gas flowstransversely through the bulk material bed, thereby cooling it. Thecooling air openings in the aerating base 3 are designed so that asufficient quantity of cooling air can be delivered but material isprevented from falling through the grate. In this case the cooling airis advantageously delivered below the aerating base 3. However, in theillustrated embodiments the air supplies are not shown in greater detailfor reasons of clarity.

The conveyor elements are divided into at least two groups, whereby theat least two groups of conveyor elements can be actuated jointly in thetransport direction of the bulk material and separately from one anotheragainst the transport direction. The detailed design and the sequence ofmovements of the conveyor elements in a first embodiment are explainedin greater detail below with reference to FIGS. 2 and 3.

In this first embodiment three groups of conveyor elements 4, 5, 6 areprovided which are disposed so that they alternate transversely withrespect to the transport direction of the bulk material (arrow 9 in FIG.1). In the illustrated embodiment six conveyor elements are providedover the width of the cooler 1, the conveyor elements 4.1 and 4.2belonging to the first group, the conveyor elements 5.1 and 5.2belonging to the second group and the conveyor elements 6.1 and 6.2belonging to the third group. Of course, within the scope of theinvention more or fewer conveyor elements can be disposed over the widthof the cooler.

Each conveyor element 4.1 to 6.2 is connected via a support element 14.1to 16.2 to suitable transport mechanisms 17.1 to 19.1. In theillustrated embodiment slots through which the support elements 14.1 to16.2 are passed are provided in the aerating base 3.

The transport mechanisms which are associated with a specific group ofconveyor elements can be coupled to one another for joint displacementof the conveyor elements. The reciprocating movement of the conveyorelements is achieved for example by way of a hydraulic drive.

The sequence of movements of the first embodiment is explained ingreater detail below with the aid of FIGS. 3a to 3 d. FIG. 3a shows thecondition after the joint forward stroke of all conveyor elements 4.1 to6.2. In this case all conveyor elements have been moved by a length a inthe transport direction of the bulk material (arrow 9). The bulkmaterial lying on the aerating base and thus also lying over theconveyor elements is displaced in a corresponding manner.

The conveyor elements are only moved back in groups or individually, sothat as little bulk material as possible is transported back again withthe return stroke of the conveyor elements. FIG. 3b shows the stateafter the return stroke of the conveyor elements 4.1 and 4.2, FIG. 3cshows the state after the further return stroke of the conveyor elements5.1 and 5.2, whilst in FIG. 3d finally the last group with the conveyorelements 6.1 and 6.2 has also been moved back.

As can be seen in particular from FIGS. 1 and 3, a plurality of conveyorelements are also disposed in the transport direction over the length ofthe cooler. The cooler elements according to the first embodiment (FIGS.2 and 3) extent substantially in the longitudinal direction, i.e. in thetransport direction of the bulk material (arrow 9).

In the second embodiment according to FIGS. 4 and 5, a plurality ofgroups of conveyor elements 4.1 to 6.2 are again provided transverselywith respect to the transport direction of the bulk material. Theconveyor elements differ from the first embodiment essentially in thatthey extend substantially transversely with respect to the transportdirection and accordingly are also supported in each case by way of twosupport elements (for example 14.1) and are connected or can beconnected to a transport mechanism (for example 17.1).

Although the conveyor elements according to the second embodiment can bealigned transversely with respect to the transport direction in theinitial position, as is the case in the first embodiment, in the secondembodiment adjacent conveyor elements are disposed in such a way thatafter each phase of movement, i.e. after the joint forward stroke andafter each individual return stroke they are oriented offset from oneanother in the transport direction.

The arrangement of the conveyor elements after each phase of movement isillustrated in FIGS. 5a to 5 d. FIG. 5a shows the state after the jointforward stroke of all conveyor elements with a stroke length a. In thiscase it may be seen that adjacent conveyor elements (transversely withrespect to the transport direction 9) are oriented offset from oneanother in the transport direction. After the first return stroke of theconveyor elements 4.1 and 4.2 of the first group an offset arrangementof adjacent conveyor elements is also produced. In FIG. 5c the conveyorelements 5.1 and 5.2 of the second group have also been drawn back andin FIG. 5d the conveyor elements 6.1 and 6.2 of the third group havebeen drawn back.

With the second embodiment the unwanted return transport of the bulkmaterial with the return stroke of the conveyor elements can be reducedeven better.

In FIGS. 6 and 7 a third embodiment is shown which essentially differsfrom the preceding embodiments by the fact that only two groups ofconveyor elements are provided, and these are moreover provided so thatthey alternate in the transport direction 9 of the bulk material.

In the representation according to FIG. 6 the front conveyor element 4.1is broken away at its two end regions in order to make visible theconveyor element 5.1 which lies behind it. Only three conveyor elements4.1, 4.2 and 4.3 and only two conveyor elements 5.1 and 5.2 of thesecond group are shown for clarification in FIGS. 7a to 7 d.

Each conveyor elements (for example 4.1) is connected via two supportselements (14.1) to a transport mechanism (17.1). In the illustratedembodiment all conveyor elements of a group are advantageously moved byway of a common transport frame.

As can be seen from FIG. 7a, the forward stroke is again carried out forboth groups of conveyor elements jointly with a stroke length a. Thestate after the return stroke of the conveyor elements 4.1, 4.2 and 4.3of the first group is shown in FIG. 7b. After the return of the conveyorelements 5.1 and 5.2 of the second group the initial state according toFIG. 7c is again achieved.

Within the scope of the invention it would also be conceivable for thestroke of the conveyor elements disposed transversely with respect tothe transport direction to be set at different lengths in the first andsecond embodiment. As a result the differences in the material bed whichare produced over the width of the aerating base can be compensated for.Thus for example the friction conditions within the bulk material in themiddle of the cooler are different from those at the two edge regions.Also a different stroke length could be utilised for better transversedistribution of the material in the starting region of the cooler.

The stroke length of the conveyor elements should be designed to beadjustable for better adaptation of the stroke length to therequirements of the particular cooler.

In all embodiments the speed for the joint forward stroke can be chosento be lower than for the return movements of the individual groups.

The aerating base preferably extends horizontally, but it would also beconceivable for it to be inclined downwards.

The material of the conveyor elements must be selected according to thetemperature occurring and the wear to be expected. Welded and castconstructions for example may be considered for this. Moreover, suitableseals should be provided in the region of the through passages for thesupport elements in order to prevent material from falling through thegrate.

The embodiments described above are distinguished in particular by thefact that the bulk material is not significantly carried along with thereturn stroke of the various groups of conveyor elements. Accordingly asmaller number of strokes is necessary for the movement of the bulkmaterial, so that in particular the wear on the conveyor elements or thetransport mechanism can also be reduced.

What is claimed is:
 1. A cooler for cooling hot bulk material,comprising: a stationary aerating base, through which cooling gas canflow, in order to receive the bulk material; and reciprocating conveyorelements disposed above the aerating base for transport of the bulkmaterial, said reciprocating conveyor elements are classified into atleast two groups of conveyor elements; wherein said at least two groupsof conveyor elements are actuated jointly in a transport direction ofthe bulk material and separately from one another against the transportdirection.
 2. A cooler as claimed in claim 1, wherein individual groupsof conveyor elements are disposed so that they alternate in thetransport direction of the bulk material.
 3. A cooler as claimed inclaim 1, wherein individual groups of conveyor elements are disposed sothat they alternate transversely with respect to the transport directionof the bulk material.
 4. A cooler as claimed in claim 1, wherein threegroups of conveyor elements are provided which are disposed so that theyalternate transversely with respect to the transport direction of thebulk material.
 5. A cooler as claimed in claim 1, wherein each of threegroups of conveyor elements is provided a number of times transverselywith respect to the transport direction.
 6. A cooler as claimed in claim1, wherein the conveyor elements which are adjacent transversely withrespect to the transport direction are disposed in such a way that,after each phase of actuation, they are oriented offset from one anotherin the transport direction.
 7. A cooler as claimed in claim 1, whereinindividual groups of conveyor elements are disposed so that theyalternate transversely with respect to the transport direction of thebulk material, a stroke of the conveyor elements being of differinglength over a width of the aerating base.
 8. A cooler as claimed inclaim 1, wherein the conveyor elements of a group can be actuatedindividually.
 9. A method of cooling hot bulk material, comprising thefollowing steps of: feeding the hot bulk material on a stationaryaerating base through which cooling gas can flow; and transporting thehot bulk material by means of reciprocating conveyor elements disposedabove the aerating base; wherein said conveyor elements are classifiedinto at least two groups which can be actuated jointly in a transportdirection of the bulk material and separately from one another againstthe transport direction.
 10. A method as claimed in claim 9, whereinafter the joint actuation of all groups of conveyor elements in thetransport direction, in each case only one group of conveyor elements isactuated against the transport direction until all groups of conveyorelements have been set back again.